Breakthrough Builds MEMS On Standard CMOS Wafer

A Spanish company, Baolab Systems, has pioneered a new technology that is expected to cut the cost of microelectromechanical systems (MEMS) while strongly impacting mobile communication design. Key to this breakthrough is the company's ability to construct nanoscale MEMS within the structure of a silicon complementary-metal-oxide-semiconductor (CMOS) wafer using standard, high-volume CMOS processing technology (see figure). This CMOS process is both rapid and easily controlled. In terms of cost, the company is predicting that the savings from using standard CMOS could be as high as 65 percent over traditional MEMS manufacturing methods.

The Baolab NanoEMS technology uses the existing metal layers in a CMOS wafer to form the MEMS structure via standard mask techniques. The inter-metal dielectric (IMD) is then etched away through the pad openings in the passivation layer using hydrogenfluoride- vapor (vHF) techniques. The etching utilizes equipment that is already available for volume production and takes less than an hour, which is a minor portion of the overall production time. The holes are then sealed and the chip is packaged as required. Because standard CMOS processes are used, NanoEMS MEMS can be directly integrated with active circuitry to suit specific applications.

Baolab has successfully created these MEMS devices using standard 0.18-m CMOS on 8-in. silicon wafers with four or more metal layers. The firm has achieved minimum feature sizes as small as 200 nm, which is an order of magnitude smaller than the sizes currently attainable with conventional MEMS. In doing so, this work brings NanoEMS MEMS into the realm of nanostructures with the subsequent benefits of smaller sizes, lower power consumption, and faster devices.

NanoEMS technology and evaluation samples will be available later this year. They target handset designers and manufacturers as well as the power-amplifier (PA) and RF front-end-module markets. In mobile-phone applications, for example, the NanoEMS devices can serve as higher-performance, lower-cost replacements for gallium-arsenide (GaAs) FETs for RF switching applications. It also can enable tunable active RF components, such as PAs and low-noise amplifiers (LNAs). This tunable capability is expected to significantly reduce the number of components needed in a mobile phone. NanoEMS products also are being developed for sensors in the mobile phone, such as electronic compasses, accelerometers, and several other functions in a single chip.